What this show is all about or not? A Theory...
"The Bothersome Man", Den brysomme mannen: Is Gravity about squaring the past?
Since this is about suicide and survivors, Miller is the anomaly in this whole series. If it was about a suicide group therapy and everything was moving to individual, but interwoven stories, wouldn’t it focus on all of them as unique stories, as it originally started, and then follow up.
Instead it focuses on Lily and Robert. And Miller’s obsesssion with them.
My theory… Miller is perhaps Lily’s dad. He’s dead (he seems to have a number of illnesses and frankly destructive habits) and all of these people are past perps, people he has seen before, people who all have to work things out as a group of suicides on the same day, same time perhaps, and he has to work all of this out until he moves onto the other side. Or, maybe it’s just about Miller and his obsession with his daughter’s choices and all those who are now around her. Or, maybe it's about them working out their issues before finally passing. Remember, this show would have concluded everthing prior to Lost's last minute, unkown ending (to dispute similarities).
Probably 100% wrong, but it’s a thought.